Wipe the chicken with paper towel and preheat the oven to 180 C / 170 FAN / Gas 5
Zest the lemon and cut the remaining lemon in half.
Place the lemon halves in the chicken and set the chicken in a roasting dish.
Mix the butter with the tarragon, garlic, salt, pepper and lemon zest.
Carefully ease away the skin from the breast meat as far as possible down to and around the legs.
Divide the butter in half and spread under the skin each side.
Cover the skin with olive oil and season with extra salt and pepper if liked.
Roast for 1 hour 40 minutes and then check to see if the chicken is cooked through.
When the chicken is cooked transfer to a serving plate and cover with foil.
Skim off the fat from the roasting pan and squeeze the juice from the lemons from the chicken into the pan.
Use a wooden spoon to loosen any crusty bits and bring the mixture to the boil on the hob.
Add the wine and allow the mixture to bubble for a few minutes to reduce.
Check the seasoning and serve with the chicken.